1. Field of the Invention
The present invention relates generally to the construction of an inhibitor switch, in which contacts are changed depending on the position of a transmission operating member in an automatic transmission for an automobile and, in particular, to an improvement of the construction of a bearing portion for a movable plate in the inhibitor switch.
2. Description of the Related Art
A conventional inhibitor switch is disclosed, for example, in Japanese Utility Model Publication No. JP-A-Hei 7-25537. This conventional inhibitor switch includes a movable plate and a movable arm which are welded in one body by ultrasonic welding. A case and a pole plate of the inhibitor switch are fixed together by means of screws and so forth.
The conventional inhibitor switch described above is assembled in the following order. In a first step, a shaft of the movable arm is inserted into an O-ring and the case of the switch. In a second step, the movable plate is mounted on the shaft of the movable arm, and a joint portion therebetween is welded by ultrasonic welding. In a third step, contact springs and movable contacts are mounted on the movable plate. In a fourth step, the case is covered by the pole plate, and these two parts are secured to each other by means of screws and so forth.
However, the conventional inhibitor switch described above has a problem in that the mounting assembly is difficult because the ultrasonic welding is effected in a state where the case is put between the movable plate and the movable arm.
Further, the inhibitor switch has a problem in that the ultrasonic welding cannot be effected all around the case because the movable arm interrupts a horn of an ultrasonic welding machine when it is tried to further join the case and the pole plate by ultrasonic welding.
In addition, there is another problem in that the shaft of the movable arm can be inadvertently welded to the pole plate by ultrasonic welding. This is caused when the movable arm and the movable plate are joined by ultrasonic welding in a state where the movable plate is put pivotably between the case and the pole plate.